[RASMB] Temperature calibration

[David Hayes]

At 12:48 PM 12/22/2004, Kirk C Aune wrote:
>I have read this thread with interest and can no longer contain myself and 
>am willing to show my vintage and detachment from the field.
>Surely, the precision of the measurements in the XL machines has been 
>established by experimentation with the same samples.   In that case, are 
>there not any Model E's available yet whereby a run can be made (where the 
>temperature accuracy is known very well by precalibration) and compare 
>that result to what is obtained in the XL machines to establish 
>accuracy?   It sure sounds like what is otherwise being proposed is overkill.
>Secondly, I find the discussion interesting because in my days of work 
>with the Model E, I was always more concerned with temperature gradients 
>in the spinning metal whereby convection could set up not only erroneous 
>temperatures, but also erroneous transport.  We messed with aluminum 
>flashing liners in the rotor chambers when we tried to do higher 
>temperature work simply out of concern for the range of heating and 
>cooling available for temperature control.   It looks like I am going to 
>have to familiarize myself more about the temperature control system of 
>these Non model E systems that are yielding modern day analytical 
>ultracentrifugation results so that I can better understand your current 
>concerns.
>
>I enjoy following all of the conversations coming through this list group.
>
>Kirk
>
>
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Hi Kirk,

I am a bit surprised myself at how prominent people in the field who 
obviously have very busy schedules are willing to undertake such a project, 
but I certainly want to follow it and contribute if I can.

I also wanted to pass on some experiences that make me interested in this 
large scale trial, perhaps because the XLA is a bit more of a "black box" 
than the old model E's.

Just as I was checking an equilibrium run at lunch today and looking at our 
data backup program when we had a power surge and the XLA lost power 
momentarily.  It beeped, and by the time I  looked at it, it had already 
regained power, rebooted and was spinning away with the error messages 
waiting to be cleared.  The software had frozen up though, so I had to 
reboot the computer, and start the XLI software (twice:  it never works the 
first time after a reboot) and restarted the absorbance scans.  Meanwhile, 
the temperature for some unexplained reason went from 4.0, where it had 
been for 3 days, to 3.5 and the controller started heating.  Of course, it 
overshot, reaching a recorded temperature of 4.8 and then slowly started to 
fall again.  As I write this, it is back to 4.2.  It makes me wonder what 
is really happening in the cells, I expect the fluctuating temperature is 
really just the surface of the rotor:  but it does point out how limited 
the temperature sensing equipment is.

At the centrifuge workshop this summer, some students brought data with 
them to analyze.  In some cases, the instructors told them:  this data just 
isn't good enough to get more information.  I have seen some differences in 
using data from our two machines with very similar samples (comparing 
absorbance scans from each), and it makes me wonder, was the sample prep 
different, or (more likely) is one of the machines just not collecting data 
as well.

Writing that last sentence reminds me to change my question to a 
request.  Please Arthur, send us enough sample to run on both machines.

I am glad that you ended with how you enjoyed reading the discussions.  I 
will not worry as much about filling people's mailboxes with email "noise", 
though maybe I have written too much on this topic.

David Hayes